How do I clear my cache on my Apple device?

To clear your Safari cache, open 'Settings' from your home screen, scroll down to the ‘Safari’ menu item and tap it, and scroll down again until you see ‘Clear Cache.' Give it a good tap and try logging in again.

If that doesn't work, I'd repeat the same steps (tap Settings then Safari), except tap "Clear Cookies" to reset any saved bits of data on your phone.